[1]} pointed out that, in principle, one of the best reddening indicators for the BLR is the He ii \(\) 1640/\(\) 4686 line ratio. Because the abundance of helium by number is a tenth that of hydrogen, and because the lines arise from very high energy levels in gas of high ionization, the He ii \(\) 1640/\(\) 4686 ratio is expected to be much less sensitive to the collisional-excitation and optical-depth effects which had been suggested to potentially drastically change hydrogen line ratios [2]}. Photoionization models of the high-ionization BLR [2]}, [4]} confirm that the He ii \(\) 1640/\(\) 4686 ratio is close to a Baker-Menzel case B value. We adopt a theoretical \(\) 1640/\(\) 4686 intensity ratio of \(8.5 \pm 1\)  for the high-ionization BLR (see Figures 2e and 3 of [4]}). The He ii \(\) 1640/\(\) 4686 ratio is not expected to vary much with physical conditions because the lines arise from high levels.
